While ad serving products can be shut down – for instance due to acquisition – such events typically happen with at least a 30 or 60-day notification to customers.
Here's the ful text of OpenX's forum post:
"OpenX’s security team is committed to the security of our services. OpenX OnRamp is a no-cost SaaS service based on our open source ad serving product (unlike our other enterprise grade offerings which run on a separate code base), which we have run as a free service to the community.
OnRamp has been the subject of escalating hacker activity in recent months, culminating in a serious attack that occurred Saturday, February 9, 2013. We have made the difficult decision to suspend the OnRamp service to protect our customers as we investigate the breach further and assess the ability of the OnRamp service to withstand future threats. At this time, we cannot predict when, or whether, the OnRamp system will be operational again.
We will post additional information in this forum as it is available. We sincerely apologize for any inconvenience caused. Other OpenX services, including OpenX Enterprise and OpenX Market, continue to operate normally."